Coating apparatus



Aug. 0, 3945. w. H. ARRETT ET AL.

COATING APPARATUS Eiled NOV. 30, 1944 3 SheeiIZS-Sheei 1 lrweniowg. William H. Boar-refit IBewmar-al KAsoieH.

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COATING APPARATUS Filed Nov. '50, 1944 5 Sheets-Sheet 2 LLI . Eermm'd K AsdelL TQR N I Aug. 2@, 1946; H, BARRETT ET AL 7 2,406,057

I COATING APPARATUS Filed Nov. so, 1944 s Sheets-Sheet s INVENTORS: Wmlliqm HjBarr-ejlf. BY Bernard KAsdell ATTORNEY Patented Aug. 20, 1946 COATING APPARATUS William newer: and Bernard K. Asdell, Inter-- national Falls, Minn, assignors to Minnesota and Ontario Paper Company, Minneapolis,

Minn.

Application November 30, 1944, Serial No. 565,926

12 Claims.

This invention relates to the art of coating sheet material and more particularly to coating webs of paper which can be processed in a continuous manner while moving at high rates of speed.

There are numerous methods of coating a web material such as paper having the desired object of applying coating that will be smooth, uniform in appearance, and of a desired Weight or thickness.

It is an object of this invention to provide an apparatus which will apply such a film of coating material to a web of paper traveling upwards of two thousand feet per minute. By the term paper as used herein, it is intended to include any and all materials in sheet form wherein a coating may be applied and treated in accordance with this invention.

Another object of this invention is the provision of a coating unit so arranged that the coating materials having wide variations in solid content may be applied to a fast moving web of paper in a predetermined weight per unit of paper.

The coating apparatus disclosed in co-pending application, Serial No. 511,753, filed November 24, 1943, provides an excellent coating on the paper, but it has the disadvantage that at speeds upward of two thousand feet when coating paper of over one hundred inches in width that the doctor roll tends to deflect. The deflection of the doctor roll at high speed tends to result in an uneven coating across the width of the sheet of paper. It has been discovered that if the doctor roll is supported between the rolls, the problem of deflection at high speed is substantially if not completely overcome.

Additional features of the invention reside in the coating fountain, the applicator roll, and provisions whereby pressure applied to the applicator roll and the doctor roll can be determined and controlled. The invention has numerous other features which will be hereinafter described in detail and particularly pointed out in the appended claims.

In the drawings forming a part of this invention, similar reference numerals indicate corresponding parts in all the drawings in which:

Figure 1 is a side elevational view of a coating apparatus;

Figure 2 is a view of a modified form of the invention;

Figure 3 is a second modification of the coating apparatus in which a nest of the driers are used in place of one large drier;

Figure 4 is a sectional viewwith parts broken away of the fountain which shows the lower nip formed by the applicator roll and the metering roll having an excess of coating material therein; and

Figure 5 is a view of the back of the fountain shown in Figures 2 and 3.

Referring to the drawings in detail: [0 indicates a web of paper coming from a source not shown; the web of paper passes roll II and then roll l2- and then into contact with the backing means or drier roll 13. The coating material to be applied to the web of paper on the backing means 13 is supplied to a fountain l4 and the surplus coating material from the fountain flows over the back side of the fountain and into a container 23. A resilient surfaced applicator roll,

I6 is so mounted that it contacts the paper upon the backing means and dips into the fountain l4. Mounted in the fountain at a selected dis tance from the applicator r011 I6 is metering roll I5 and it is generally preferred that the metering roll be a hard surfaced unit. This metering roll controls the amount of coating material which is carried by the applicator roll l6. Immediately above the applicator roll at a selected distance therefrom is mounted a hard surfaced doctor roll IT. This doctor roll removes a portion of the coating material on the applicator roll I6 and smooths upon the' applicator rolls periphery the coating material remaining thereon. The doctor roll I! is generally a hard surfaced roll and has its periphery wiped substantially clean by a resilient surfaced roll 18 which is mounted immediately above the doctor roll. To remove the coating from the resilient surfaced roll, a doctor blade I9 is provided. The coating material removed by the doctor blade is returned through trough like member and pipe 2| to coating container 23. The coating material in the container 23 is withdrawn by pump 25 and forced through pipe 26 and into fountain [4 adjacent the top of the fountain.

When applying coating of ten pounds or more per side to a web of paper, it is preferred that such coating be applied in two applications rather than in a single application. As disclosed in Figure 1, coating units generally indicated at 40,.

4], 42, and 43 are of identical construction as that herein described.

The paper [0 after having the coating applied by applicator roll I6 of coating unitlo' passes around a substantial portion of the surface of the drier l3. After the coating has'at least preliminarily set, a felt is brought in contact with the paper for a portion of its travel over the drier surface. Some of the reasons for the use of the felt is to prevent drier wrinkles, and to hold the paper in close contact with the drier surface. 35 and 36 and then comes in contact with the coated paper. The felt leaves the surface of the paper at roll 28 and the paper and the felt travel together over rolls 30, 3| and 32.

The paper then receives its second film on the same side by coating unit 4| and then passes around drier roll 37. The paper leaves the drier roll at roll 46. The felt 54 contacts the paper on a portion of its travel around the surface of the drier 31 and this felt leaves the surfaceof the paper at roll 45 and then the paper and the felt travel together over rolls 41 and 48 The felt which is endless then passes over rolls 49, 59, and 5|. then is carried by felt 53 over rolls 54, 55 and 56. The felt 53 then travels over rolls 5T, 58, and 59. The coated paper after leaving felt 53 passes in contact with roll 60 and thenreceives its first coating on the opposite side by coating unit 43. The coated paper travels around a substantial the drier surface at roll 64. The'felt 5! which contacts the paper on thes'urface 'of the drier 39 passes 'over roll 63 after leaving the surface of the paper on the drier. The paper travels with felt BI over rolls' 65, 65, and 6?. The endlessfeltfil then passes over rolls 59, I0 and 62, then back in contact with the coated surface of the paper. The paper after leaving the roll 6? passes around the surface of the drier 39 and receives its second coating on the opposite side of the sheet by coating unit: 42. The coated paper is contacted on a portion of the drier surface 38. by felt II. The felt parts. contact with the surface'of the coated paper at roll I3. for a space while the coated paper travels 'to and around the roll I4 and thereafter the felt and paper pass over rolls 15, I6, and IT. The paper then passes over roll 8i to suitable means not shown, for winding in rolls; 4

In Figure 2 of the drawings, thereis shown a modification of the apparatus disclosed in Figure 1, and in this modification, the paper I9 passes over rolls II and I2, and then into contact with the surface of a heated drying roll. The paper after traveling over 'a'portion of the surface of the drier roll leaves that surface and passes over a jump roll I03 and then back into contact with the drier surface. The paper leaves the surface of the drier at roll 29.' The coated surface of the paper is contacted on aportion of its travel over the'd'rier surface with a positively driven felt. The purpose of this felt is to eliminate to a great extent, if not completely, the formation of drier wrinkles and also to hold the coated paper in close contact with the drier surface. The endless felt leaves the surface of the coated paper and passes over roll'28' where the coated paper and the felt travel together for a given distance.

In the coating of paper on the felt side, it sometimes occurs that, this surface of the paper is resistant'to the absorptionof moisture, and the moisture from the coating material does not uniformly wet the paper; This difiiculty may be overcome by lightly brushing the surface of the paper. This is accomplished, in Figure 2 by' hav-' ing the surface of the paper lightly contacted with the surface of the roll I8.

The coating material is pumped from a suitable coating container to a fountain wherein a pond,

The felt passes over rolls 33, 34, and v 4 of coating material is maintained with a head higher than the nip formed by the applicator roll and the metering roll. The excess coating from the fountain shown in Figure 1 is returned to the container by pipe 22. A resilient surfaced applicator roll l5 rotates into the fountain and picks up coating in excess to that to be applied to the paper. A metering roll or doctor roll I5 which is positioned at a selected distance from the applicator roll surface l6 controls the amount of coating on the applicator roll. The coating on the applicator roll after passing metering roll I5 is smoothed and a portion removed by rotating hard surfaced doctor roll H. The hard surfaced doctor roll may be composed of various materials but it is believed essential that the hardness of the doctor roll I1 be considerably harder than that of the resilient applicator roll IS. The coating The paper continues over roll 52 and material removed by doctor roll IT is wiped from the surface of this roll by resilient surfaced roll I8 and any coating material removed by the roll I8 is doctored therefrom and returned to the coating container.

The rolls I6 and H are supported by upright member which is pivoted at 84. The doctor roll I 5 is supported by a member which is pivoted at 91. The purpose of the pivot of doctor roll and the applicator roll is to permit separation of the applicator roll from the doctor roll and the doctor roll from the drier surface. To control the amount of pressure applied by metering roll or doctor roll I5 to the resilient applicator surface I5 is a pressure adjusting rod 88 secured to the metering roll support. This rod is connected to an eccentric 89 and extending from this eccentric 89 is'handle 99. By turning the handle 90 the pressure between the rolls I5 and I5 can be controlled and varied. A member 9| is hingedly connected to the member 85 at 92, and this member'is pivotally connected to upright member 94 at 93. The upright member 94 is pivoted at one end of 95 and connected at the other end to member 96. The member 96 is connected with a hydraulic or other power cylinder 9'! for varying the pressure of the coating unit against the drier surface. For supporting the roll I8 is member 98 secured to the'roll and pivotally secured to the upright member 94 at 99. For varying the pressure between the rolls I6, I7, and I8 there is provided a member I99 which connects member 9| and 98 through the medium of eccentric IIH. For turning the eccentric there is provided a handle I92 whereby the pressure between these rolls may be varied and controlled.

Although the contact of the coated paper with the drier surface in the modification shown in Figure 2 is less than that shown in Figure 1-, the rate of speed of drying is expedited by the fact that the steam generated in the drying coated paper is permitted to be dissipated while the paper is out of contact with the drier surface.

In Figure 3 is shown another modification wherein the single drying roll is replaced by a nest of drying rolls. The paper ID in this modification as it passes over roll Ila, which in some cases is heated so as to bring the temperature of the paper to be coated to approximately the temperature of the coating material. In this modification, the backing roll I95 contacts the paper as the coating is being applied by resilient roll IS. The paper after being coated passes around the surface of drying rolls I06, I61, I98, and I09. 'At the drying roll I09, the coating surface of the paper is in contact with the heated surface. It is to be understood that the nest of rolls may vary in size from each other and in number depending uponthe amount of drying surface necessary to set the coating material.- Also, a nest of drying rolls has the advantage over a single drying roll in that it permits a controlled temperature to be used in the drying of the coatingmaterial. For example, the temperature on roll I06 may be from 225-275" F., while the temperature of roll I01 may be varied from 275-325 F., and the tem-' perature of the roll I08 may be varied from 325- 375 F. While the temperature of the roll I09 may be considerably above the temperature of the other rolls without resulting in damage to the coated surface. The coating material is supplied to the container 23 and this coating is removed by pump 25 and passes through line 26 into the fountain M. A- sufficient head of coating material is maintained in the fountain l4 so that the lower nip of the metering roll and the applicator roll is flooded. Thisassures that foaming of the coating material will be substantially if not entirely eliminated. The coating material on the resilient surfaced applicator roll 16 after it passes the metering roll is smoothed and a portion of it removed by hard surfaced doctor roll H. A portion of the coating material on the surface of the doctor roll I1 is removed by resilient surfaced roll M which has its surface cleaned by a suitable doctor blade and the coating material so removed is returned to the coating container 23. The direction of rotation of the rolls is disclosed in Figure 3, and the direction of rotation is the same in each of the apparatus shown. It may be pointed out that the surplus coating material is pumped to the fountain and the back of the fountain is lower than the side walls for permitting the coating material to flow over the back of the fountain l4 and return to the coating container 23.

When using mineral-adhesive coating material it is preferred that the solids content of the coating material be above 60% solids, and generally within the range of about 61% to 75% solids. The apparatus and process herein disclosed permits the coating of paper from about four hundred feet per minute to about two thousand feet per minute without changing the viscosity or other characteristics of the coating material.

It is to be understood that changes, modifications, etc., may be made by those skilled in the art without departing from the spirit of the invention as described herein.

What is claimed:

1. In a coating unit including a backing means, an applicator roll for transferring coating material to a material to be coated supported by the backing means, a fountain having an open side directed toward the applicator roll so that the fountain and the applicator roll form a coating container, a metering roll mounted in the fountain at a selected distance from the applicator roll, and a doctor roll above the applicator roll at a selected distance therefrom.

2. A coating apparatus including a backing roll, an applicator roll for transferring coating material to a moving web supported by the backing roll, a fountain having on open side directed toward the applicator roll so that the fountain and applicator roll form a coating container, a doctor roll above the applicator roll at a selected distance therefrom, and a roll mounted above the doctor roll and contacting the surface of the doctor roll.

3. A coating unit including a backing cylindrical member, a fountain, an applicator roll re- 6 ceiving'coat-ing from the fountain, 'a metering roll at a selected distance from the applicator roll, a doctor rollabove the applicator'roll at'a selected distance therefrom, and a roll above the doctor roll and contacting the surface of the doctor roll.

4. A coating apparatus comprising,- a backing roll, an applicator roll having a surface with resilient properties, a fountain having an open side directedtoward the applicator rollso that the fountain and the applicator roll form a coating container, a hard surface metering roll mounted in the fountain at a selected distance from the applicator roll, a doctor roll above the applicator roll at a selected distance therefrom, and a roll for cleaning thesurface of the-doctor roll.

.5. A coating unit including a, backing cylindrical member, a fountain, an applicator roll receiving coating from the fountain, a metering roll at a selected distance from the applicator roll, a doctor roll above the applicator roll, and at a selected distance therefrom, and means for separating the metering roll from the applicator roll, and means of separating the applicator roll and the backing roll.

6. A coating apparatus comprising, a backing roll, an applicator roll with a surface having resilient properties, a fountain having an open side directed toward the applicator roll so that the fountain and the applicator roll form a coating container, a metering roll mounted in the fountain at a selected distance from the applicator roll, a doctor roll above the applicator roll and at a selected distance therefrom, a roll above the doctor roll for cleaning the surface of the doctor roll, and means for cleaning the surface of the roll cleaning the surface of the doctor roll.

'7. A coating apparatus comprising, a backing roll, an applicator roll for transferring coatin material to a moving web of paper, a fountain having an open side directed toward the applicator roll so that the fountain and the applicator roll form a coating container, a doctor roll above the applicator roll and at a selected distance therefrom, a roll mounted above the doctor roll and adapted to contact the surface of the doctor roll, and a doctor blade for cleaning the surface of the roll that contacts the surface of the doctor roll.

8. In a coating apparatus comprising, a backing means for supporting a moving web of paper; resilient surfaced applicator roll for transferrin coating material to paper supported between the backing means and said roll, a fountain having an open side directed toward the applicator roll so that the fountain and the applicator roll form a coating container, a metering roll mounted in the fountain maintained at a selected distance from the applicator roll, a doctor roll above the applicator roll and at a selected distance therefrom, a roll mounted above the doctor roll for contacting the surface of the doctor roll, means for cleaning the surface of the roll that contacts the doctor roll surface, and means for returning the coating material to the fountain removed from the roll contacting the surface of the doctor roll.

9. A coating apparatus comprising, a backing roll, an applicator roll for applying coating material to a traveling web of paper, a fountain having an open side directed toward the applicator roll so that the fountain and the applicator roll form a coating container, a metering roll mounted in the fountain at a selected distance from the applicator roll, a doctor roll mounted above the applicator roll and at a selected distance therefrom; a roll for cleaning the surface, of they doctor rolLand means for controlling the pressure between the applicator roll, the doctor roll and the roll for cleaning the doctor roll surface.

10. In combination with a nest of coated paper driers, a backing means, a fountain having an open. side, an applicator roll for rotating into and out of the fountain at the open side, a metering roll mounted in the fountain at a selected distance from the applicator roll, a doctor roll mounted above the applicator roll and at a selected distance therefrom, and means for cleaning the surface of the doctonroll. A

11. In a coating apparatus comprising, a backing means, an applicator roll having a surface with resilient propertiesa fountain having an openside directedtoward the applicator roll so that t e applicator roll and the fountain form a coating container, a hard surfaced metering roll mounted in the fountain at a selected distance from the applicator roll, a hard surfaced doctor roll mounted above the applicator roll and at a selected distance therefrom, and a resilient surfaced roll mounted above the doctor roll for cleaning the surface of the doctor roll.

12. A coating unit including a backing roll, an applicator roll for transferring coating material to a web of paper and the like supported by the backing roll, a fountain having an open side directed toward the applicator roll so that the fountain and the applicator roll form a coating container, a metering roll at a selected distance from the applicator roll for controlling the amount of coating material carried by the applicator roll from the coating container, and a doctor roll at a selected distance from the applicator roll for smoothing the coating on the said applicator roll.

WILLIAM H. BARRETT. BERNARD K. ASDELL. 

